In an image forming apparatus such as an electrophotographic device, and an electrostatic recording device, an image is formed by developing a latent electrostatic image formed on a photoconductor with a toner to form a toner image, and transferring the toner image to a recording medium such as paper, followed by fixing the toner image thereon with heat. For forming a full color image, developing is generally performed using toners of 4 colors, i.e. black, yellow, magenta, and cyan. In this case, a toner image formed of a toner of each color is transferred to a recording medium to superimpose all the toner images, and then fixed thereon with heat.
In the course of the preparation of full-color images, there is a problem that heat resistance storage stability of a toner lowers as low temperature fixing ability of the toner is improved.
To counter this problem, PTL1 discloses a core-shell structured toner containing a releasing agent, a colorant, a binder resin and filler, as a toner for developing latent electrostatic images. This toner has the ½ outflow temperature of 60° C. to 100° C. as measured by a flow tester, and the shell of the toner contains a thermoplastic resin.
The disclosed toner however has a problem that low temperature fixing ability of the toner, inhibition of toner spent, and hot offset resistance of the toner cannot be achieved at the same time in high temperature and high humidity environments.